http://gcmd.nasa.gov/r/l/TermsOfUse9.1.52020-05-26 17:10:52MBTThe mechanical bathythermograph was the predecessor to the
expendable bathythermograph which remains a cornerstone in ships
of opportunity sampling today. This instrument was used to
obtain continuous tracings of temperature versus depth in the
surface layers of the ocean.
[Summary provided by NOAA]